Julie Verheyen

Warming is increasingly recognized to magnify the toxicity of chemicals. Yet, limited understanding of the underlying physiological mechanisms constrains our ability to predict these interactions between warming and toxicants, and how these may evolve under global climate change scenarios. Here, a common-garden experiment was conducted with two resurrected subpopulations of Daphna magna, separated by ca. 40 years in time, of which the recent subpopulation evolved a higher heat tolerance. Daphnia were exposed to low (150 µg L-1) and high (300 µg L-1) zinc levels across a large thermal gradient (12 °C - 30 °C). After 96-h exposure, bioenergetic traits, oxidative damage to lipids and hemoglobin levels were quantified. Both zinc levels caused stronger reductions in net energy budget at higher temperatures in both subpopulations. At the highest temperature, low zinc reduced energy consumption in the old subpopulation, whereas the recent subpopulation evolved an increased energy consumption, resulting in a greater decline in the net energy budget. Across treatment groups, survival correlated positively with the net energy budget, and negatively with oxidative damage, while the hemoglobin levels correlated positively with the acute heat tolerance. These findings suggest reductions in the net energy budget to be a key driver of the widespread phenomenon whereby toxicants become more lethal at higher temperatures, and reductions in hemoglobin to contribute to the toxicant-induced declines in heat tolerance. Overall, our study underscores the importance of incorporating physiological mechanisms to understand and predict the current and future sensitivity of organisms to contaminants under ongoing climate change.

Latitudinal patterns in fitness‐related traits within species are receiving increased attention as these inform how high‐latitude populations may evolve in response to global warming. The underlying mechanisms for these latitudinal trait patterns remain poorly understood, and recently the gut microbiome has been suggested to be a potentially important proximate driver of these patterns. We investigated the novel idea of whether the gut microbiome drives latitudinal differences in immune function and pathogen load. To test this idea, we performed a reciprocal gut microbiome transplant between slow‐paced, high‐latitude (southern Sweden) and fast‐paced, low‐latitude (southern France) populations of Ischnura elegans damselflies. The transplants were conducted in the laboratory between high‐ and low‐latitude larvae, at both a colder and warmer thermal regime, whereafter larvae were exposed to Escherichia coli, a widespread pathogenic bacterium in aquatic ecosystems. During the experiment, larval mortality, growth rate, phenoloxidase (PO) level (a measure of immune function), E. coli burden (a measure of pathogen load) and the gut microbiome diversity (α‐diversity) and community compositions (β‐diversity) were analysed. Exposure to the pathogen increased mortality, especially under warming. Our results confirmed latitude‐associated thermal adaptation and a faster pace of life of the low‐latitude larvae, which was associated with a lower immune function (lower activity of PO), consistent with previous findings and now showed this to be linked to a higher pathogen load (higher E. coli body burden). Moreover, our results provided the first experimental evidence that the gut microbiome causally contributed to latitudinal differences in the host's immune function and pathogen load. As latitudinal patterns in the microbiome are widespread, this may be an important yet ignored proximate driver of the latitudinal patterns in immune function and pathogen load.

Explaining interspecific differences in pesticide sensitivity is key to increasing the predictive power of ecotoxicology. Besides species traits, the gut microbiome may provide an untested additional predictive factor since it often plays a role in host defense against stressors. Therefore, we investigated the gut microbiome's causal role in shaping differences in pesticide sensitivity between two congeneric damselfly species. After an antibiotic treatment, reciprocal gut microbiome transplants were performed between pesticide-sensitive Ischnura elegans and more tolerant Ischnura pumilio larvae, with donor larvae first preexposed to either chlorpyrifos or a solvent control to match the subsequent pesticide treatments of the recipients. The gut microbiome, determined by 16S rRNA gene amplicon sequencing, of both species included pesticide-degrading bacteria, but also showed shared and species-specific responses to the pesticide. Notably, the most pesticide-sensitive combination, with the highest pesticide-induced mortality, consisted of I. elegans larvae receiving I. elegans donor gut microbiota, whereas the least sensitive combination consisted of I. pumilio larvae receiving I. pumilio donor gut microbiota, whereby the pesticide did not increase larval mortality. The two mixed donor-recipient gut microbiome combinations resulted in an intermediate sensitivity. Remarkably, I. elegans recipient larvae experienced a lower chlorpyrifos-induced mortality when they received an I. pumilio donor gut microbiome than when they received their conspecific I. elegans donor gut microbiome. Our results provide, to our knowledge, the first proof-of-evidence that the gut microbiome causally contributes to species differences in pesticide sensitivity.

Freshwater snails are pivotal in transmitting schistosomiasis, a tropical parasitic disease affecting over 150 million people. The adaptive potential of these snails is a critical factor in determining how climate change and other environmental factors influence disease transmission dynamics, yet it has remained unexplored. Bulinus truncatus is the schistosome intermediate host snail with the widest geographic distribution and therefore plays a pivotal role in determining the maximum range of urogenital schistosomiasis. In this study, we assessed the local adaptation capacity of B. truncatus to temperature through an integrative approach encompassing phenotypic, ecophysiological, and genomic data. Ten snail populations from diverse thermal environments were collected in three countries, with eight populations reared in a common garden. The F2 generation (total N= 2592) was exposed to eight chronic temperature treatments and various life-history traits were recorded for over 14 weeks. Subsequently, ecophysiological analyses were conducted on the ten last surviving snails per population. Genotyping the parental generation collected in the field using a genotyping-by-sequencing (GBS) approach, revealed 12,875 single nucleotide polymorphisms (SNPs), of which 4.91 % were potentially under selection. We observed a significant association between these outlier SNPs, temperature, and precipitation. Thermal adaptations in life-history traits were evident, with lower survival rates at high temperatures of warm- origin snails compensated for by higher reproduction rates. Cold-origin snails, on the other hand, exhibited higher growth rates adapted to a shorter growing season. Ecophysiological adaptations included elevated sugar and haemoglobin contents in cold-adapted snails. In contrast, warm-adapted snails displayed increased protein levels but also more oxidative damage. Furthermore, heightened phenoloxidase levels indicated a more robust immune response in snails from parasite-rich regions. The substantial local adaptation capacity of B. truncatus holds profound implications for its response to climate change, future schistosomiasis risk, and the effectiveness of schistosomiasis control measures. Highlights: Local adaptation influences species’ responses to climate change The snail Bulinus truncatus showed a high thermal local adaptation (LA) potential LA is apparent through variations in life history and ecophysiological traits We identified a significant genetic basis underlying this LA LA of the hosts could sustain schistosomiasis transmission under global warming

The Society of Environmental Toxicology and Chemistry (SETAC) convened a Pellston workshop in 2022 to examine how information on climate change could be better incorporated into the ecological risk assessment (ERA) process for chemicals as well as other environmental stressors. A major impetus for this workshop is that climate change can affect components of ecological risks in multiple direct and indirect ways, including the use patterns and environmental exposure pathways of chemical stressors such as pesticides, the toxicity of chemicals in receiving environments, and the vulnerability of species of concern related to habitat quality and use. This article explores a modeling approach for integrating climate model projections into the assessment of near- and long-term ecological risks, developed in collaboration with climate scientists. State-of-the-art global climate modeling and downscaling techniques may enable climate projections at scales appropriate for the study area. It is, however, also important to realize the limitations of individual global climate models and make use of climate model ensembles represented by statistical properties. Here, we present a probabilistic modeling approach aiming to combine projected climatic variables as well as the associated uncertainties from climate model ensembles in conjunction with ERA pathways. We draw upon three examples of ERA that utilized Bayesian networks for this purpose and that also represent methodological advancements for better prediction of future risks to ecosystems. We envision that the modeling approach developed from this international collaboration will contribute to better assessment and management of risks from chemical stressors in a changing climate. Integr Environ Assess Manag 2024;20:367–383. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).